The following recommendations refer to the application and maintenance of various types of other well control equipment: chole manifold,  

Inside pipe shut-off tools, Mud-gas separator and trip tank, Mud pit level indicator and recorder,c High pressure mud and cement system, Storm chokes.

1 Choke manifold

For working pressure ratings over 13,800 kPa (2000 psi), the choke manifold shall be constructed in accordance with Company's procedure.

Alternatively, a choke manifold as already installed by the owner of the drilling unit may be acceptable, but only if approved in writing by the Company Rig Superintendent.

Whilst drilling, the block valves upstream of both chokes and valves downstream of the remote choke to the mud-gas separator shall be in an open position.

The remote choke shall be in an open position and the adjustable choke, shall be left in a closed position.

The remote choke is operated from a control panel installed near the driller's position.

The minimum recommended size for all choke lines and valves is 76.2 mm (3") through bore. Valve size and line bore size of BOP stack side outlets and valves, choke lines and choke manifold should be identical throughout the system.

Choke manifolds rated to 103,500 kPa (15,000 psi) shall have hydraulically operated valves upstream of any choke to assist in opening/closing valves under pressure quickly, thus minimising gate and seat wear.

Chokes should incorporate a suitable bleeder valve facility to ensure that the pressure can be released prior to removal of the bonnet nut. Hammer type threaded bonnet nuts are not recommended. Flanged or bonnet clamp connections are preferred.

Temperatures downstream of the choke are to be limited to the design temperature rating of the choke manifold.

2 Inside pipe shut-off tools

Two lower kelly cocks for each size of drillpipe in use shall be available, one of which shall be used below the kelly or top drive during drilling operations and the other shall be on the drilling floor complete with removable handles for easy stabbing and connecting.

Subs for connecting the kelly cock to DCs in use shall also be available on the drilling floor.

Two drop-in type back-pressure valves must be available. These to be complete with seating subs to fit the drillstring in the hole. The drop-in valves must be able to pass the smallest bore in the drillstring above the seating sub, and preferably be wireline retrievable.

A 'Gray-type' inside BOP, with the appropriate connections for the drillstring in use, shall be on the drilling floor at all times. It shall be ready for immediate use.

The left-hand threaded upper kelly cock shall be in good operating condition at all times. A test sub for testing the kelly or top drive and kelly cocks shall be available on the drilling rig.

The upper and lower kelly cock of a top drive should be hydraulically operated.

It should be possible to break the connection above the lower kelly cock of the top drive and remove the top drive when string entry below the top drive is required with the well under pressure.

A 10,000 psi WP 3" rotating type circulating head with correct bottom subs for the drillstring sizes in use shall be available on the drilling floor.

A casing circulating head with a pressure rating equal to the casing rating shall be available on the drilling floor throughout casing running operations.

An optional item is a fast shut-off coupling (Regan type) for use in an emergency on the drilling floor. If available, it shall match the tool joints in use and be fitted with a kelly cock in the open position. It should be tested on the same routine frequency as the BOP stack.

3 Mud-gas separator and trip tank

The mud-gas separator separates the free gas from the contaminated mud leaving the choke manifold before it is routed to the degasser. Entrained gas is extracted at the degasser.

The mud-gas separator can be installed as:

• a skid mounted horizontal or vertical unit outside a mud tank;
• united with the trip tank.

The size of the mud-gas separator should be such that it can handle the fluid and gas which is bled off via the choke manifold safely. Minimum dimensions and configurations of various types of mud-gas separators are given in (click link).

The following shall be met when configurating the pipework for the mud/gas separator:

• there are to be no valves, pipe expansion or contractions within 3 m (10 ft) of the inlet nozzle;
• if a bend is required in the feed pipe it shall be in a vertical plane through the axis of the feed nozzle;
• the pipe reducer of the gas outlet line should be no nearer to the top of the vessel than 0.6 m (2 ft).

The gas outlet line shall be a minimum of 200 mm (8"). If the vent exists more than 40 m (130 ft) from the vessel this vent line diameter should be increased to ensure that the back pressure in the vent line does not exceed 15 kPa (2 psi), at a gas flowrate of 0.2 x 106 m3 (st)/d (7 MMscf/d). No reduction in any vessel dimension is permitted.

No other internals (e.g. mist mats) are permitted due to their unsuitability for the rugged service.

The mud-gas separator shall have one or more vent lines leading a safe distance downwind from the well, and/or to the top of the derrick. Low places in the vent lines should be avoided in order to prevent liquids being trapped in them.

Never connect the choke manifold and/or mud-gas separator discharge lines directly to the degasser (always have an open pipe).

Equivalent vendor mud-gas separators are acceptable if they comply with the basic design criteria.

The mud-gas separator shall not be operated above its design limitation. Operating outside of this envelop will give poor mud/gas separation and the possibility of gas blow through. An additional unit with dedicated vent line shall be installed when the mud-gas separator capacity is insufficient for the well to be drilled.

The trip tank shall be provided with an accurate fluid level indicator or a recorder/indicator, showing the amount of mud used to keep the hole full when pulling pipe, and the amount of mud returned when running in.

4 Mud pit level indicator and recorder

An indicating and recording mud pit level system, capable of providing early visual and audible warning of gain or loss of fluid in the well, shall be installed in those mud tanks which serve as active mud tanks.

The complete system must be kept in proper working condition at all times. An indicator or recording chart must be easily visible to the driller.

5 High pressure mud and cement system

Prior to spudding, the drilling mud pumps, mud manifolds, valves and main discharge lines shall be pressure tested with water to 5000 psi.

The emergency high pressure kill pump (and/or the cement pump), manifolds, valves and lines shall be tested to the maximum rated working pressure of the lowest rated part of the system.

6 Storm chokes

The storm choke comprises of a retrievable packer to support the weight of the drillstring and seal off the casing, and above this a combination back-off tool/valve, to seal the drillstring.

When a subsea BOP stack is in use, storm chokes shall be available, sized to match the casing and drillpipe in use.

The equipment is used when it is necessary to work on the BOP equipment, or when it is too hazardous to rack pipe in the derrick during adverse weather conditions.